Soils are alive with a fantastic number of many types of organisms, most of which help to grow healthy plants and protect them from pests. The food for all the soil’s organisms originates with crop residues and organic materials added from off the field. These provide the fuel that powers the underground life that has such a positive effect on the soil’s chemical and physical properties, as well as, of course, maintaining a system of equilibrium that helps regulate the populations of organisms. Soil organisms are associated with each other in a balance in which each type of organism performs specific roles and interacts with other organisms in complex ways. When there is an abundance of food and minimal soil disturbance, the complex food web that exists helps to maintain a self-regulation of organisms as bacteria and protozoa eat bacteria and some fungi, nematodes eat bacteria and fungi (as well as other nematodes and plant roots), fungi eat nematodes, and so on up the food web. We should be trying to use management practices that promote a thriving and diverse population of soil organisms.


Alexander, M. 1977. Introduction to Soil Microbiology, 2nd ed. New York: John Wiley.

Avisa, T.J., V. Gravelb, H. Antouna, and R.J. Tweddella. 2008. Multifaceted beneficial effects of rhizosphere microorganisms on plant health and productivity. Soil Biology and Biochemistry 40: 1733–1740.

Behl, R.K., H. Sharma, V. Kumar, and N. Narula. 2003. Interactions amongst mycorrhiza, azotobacter chroococcum and root characteristics of wheat varieties. Journal of Agronomy & Crop Science 189: 151–155.

Dindal, D. 1972. Ecology of Compost. Office of News and Publications, 122 Bray Hall, SUNY College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, NY.

Dropkin, V.H. 1989. Introduction to Plant Nematology. New York: John Wiley.

Garbeva, P., J.A. van Veen, and J.D. van Elsas. 2004. Microbial diversity in soil: Selection of microbial populations by plant and soil type and implications for disease suppressiveness. Annual Review of Phytopathology 42: 243–270.

Hendrix, P.F., M.H. Beare, W.X. Cheng, D.C. Coleman, D.A. Crossley, Jr., and R.R. Bruce. 1990. Earthworm effects on soil organic matter dynamics in aggrading and degrading agroecosystems on the Georgia Piedmont. Agronomy Abstracts, p. 250. Madison, WI: American Society of Agronomy.

Ingham, E.R., A.R. Moldenke, and C.A. Edwards. 2000. Soil Biology Primer. Soil and Water Conservation Society and USDA Natural Resource Conservation Service. sqi/concepts/soil_biology/biology.html.

Kennedy, A.C., T.L. Stubbs, and W.F. Schillinger. 2004. Soil and crop management effects on soil microbiology. In Soil Organic Matter in Sustainable Agriculture, ed. F.R. Magdoff and R. Weil, pp. 295–326. Boca Raton, FL: CRC Press.

Paul, E.A., and F.E. Clark. 1996. Soil Microbiology and Biochemistry, 2nd ed. San Diego, CA: Academic Press.